What the label lists and what reports show

Sulfasalazine side effects

Sulfasalazine's FDA label: “The most common adverse reactions associated with sulfasalazine are anorexia, headache, nausea, vomiting, gastric distress, and apparently reversible oligospermia.” FAERS holds 77,784 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is pain (15,947 reports).

Generic listed

Check it at the source: the sulfasalazine FDA label on DailyMed (effective May 29, 2026, Pfizer Laboratories Div Pfizer Inc); the FDA FAERS public dashboard.

What does the label list?

From the label: adverse reactions
The most common adverse reactions associated with sulfasalazine are anorexia, headache, nausea, vomiting, gastric distress, and apparently reversible oligospermia.

From the label: adverse reactions, continued
The most common adverse reactions associated with sulfasalazine are anorexia, headache, nausea, vomiting, gastric distress, and apparently reversible oligospermia. These occur in about one-third of the patients. Less frequent adverse reactions are skin rash, pruritus, urticaria, fever, Heinz body anemia, hemolytic anemia, and cyanosis, which may occur at a frequency of one in every thirty patients or less. Experience suggests that with a daily dosage of 4 g or more, or total serum sulfapyridine levels above 50 µg/mL, the incidence of adverse reactions tends to increase. Although the listing which follows includes a few adverse reactions which have not been reported with this specific drug, the pharmacological similarities among the sulfonamides require that each of these reactions be considered when AZULFIDINE Tablets are administered. Less common or rare adverse reactions include: Blood dyscrasias: aplastic anemia, agranulocytosis, leukopenia, megaloblastic (macrocytic) anemia, purpura, thrombocytopenia, hypoprothrombinemia, methemoglobinemia, congenital neutropenia, and myelodysplastic syndrome.

Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective May 29, 2026 (SPL set ddbe69f3-bd55-45f3-a64f-f60226c744c4), via openFDA; the full label on DailyMed

What do FAERS reports show?

77,784 reports list sulfasalazine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 7,233 are coded as a death and 21,393 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 20 reactions below, 5 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.

Reports received each year

The 25 most reported reactions

Drug Ineffective (a use or a product term, not a reaction)29,357
Rheumatoid Arthritis (a use or a product term, not a reaction)19,529
Pain15,947
Drug Intolerance13,762
Arthralgia (named in the label)13,481
Fatigue13,318
Joint Swelling12,744
Off Label Use (a use or a product term, not a reaction)11,129
Rash (named in the label)10,987
Abdominal Discomfort10,045
Contraindicated Product Administered9,681
Condition Aggravated (a use or a product term, not a reaction)9,593
Alopecia (named in the label)9,474
Synovitis9,222
Arthropathy9,216
Treatment Failure (a use or a product term, not a reaction)8,899
Systemic Lupus Erythematosus8,877
Swelling8,705
Nausea (named in the label)8,586
Drug Hypersensitivity8,460
Pemphigus8,068
Glossodynia7,851
Hypersensitivity (named in the label)7,607
Hand Deformity7,498
Musculoskeletal Stiffness7,470

Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms

What next?

Sulfasalazine: the full record: label, generics, price, shortages, recalls
Report a side effect to the FDA: MedWatch
Side effects hub: the most reported medicines and reactions